JPWO2005096278A1 - Information recording apparatus, information recording method, and information recording program - Google Patents

Abstract

Provided are an information recording apparatus, an information recording method, and an information recording program capable of recording information with less waveform distortion with an appropriate modulation degree and high asymmetry. The information recording apparatus records information by irradiating a recording medium such as DVD-R / RW or DVD + R / RW with a laser beam to form a recording mark corresponding to the recording signal. The recording pulse signal for forming the recording mark corresponding to the recording signal has a mark period for forming the recording mark and a space period for not forming the recording mark. In test writing (test recording) performed prior to actual information recording, the recording power of the long mark is made constant and the recording power of the short mark is changed. Preferably, the recording power of the short mark during the test writing is changed so that the asymmetry and / or the β value is in a desired range. Thereby, the recording power of the short mark is appropriately determined so as to obtain desired recording characteristics. Further, actual recording is performed using the recording power thus determined.

Description

  The present invention belongs to a technique for recording information on an optical disk using a laser beam or the like.

  In a writable or rewritable optical disc such as a DVD-R (DVD-Recordable) and a DVD-RW (DVD-Re-recordable), information is recorded by irradiating a laser beam on the recording surface of the disc. In the portion irradiated with the laser beam on the recording surface of the optical disc, the temperature rises, so that the optical recording medium constituting the optical disc changes, whereby a recording mark is formed on the recording surface.

  Therefore, the laser beam is modulated with a recording pulse having a time width corresponding to the information to be recorded, and a laser pulse having a length corresponding to the signal to be recorded is generated. A recording mark having a length corresponding to the information can be formed on the optical disc.

  On the other hand, recently, a laser power control method has been used in which a recording mark is formed by a pulse train portion (also called a pulse train) including a plurality of short pulses, instead of forming one recording mark by one laser pulse. . For high-speed recording, a method of using a recording pulse waveform composed of a top pulse period, a last pulse period, and an intermediate bias period therebetween instead of a recording pulse waveform including a pulse train has been proposed. (See, for example, Patent Documents 1 and 2).

  In the above recording method, the laser power in the pulse train period, top pulse period, last pulse period, etc. has a fixed value regardless of the mark length. For example, in a write strategy for 8-times speed recording of DVD-R, 3T and 4T marks are recorded by a single recording pulse, and marks of 5T or more are between the top pulse period, the write pulse period, and the intermediate period as described above. Recording is performed with a recording pulse waveform having a bias period, but their levels, that is, the recording power is the same.

  On the other hand, in the 4 × speed recording system of DVD + R, all length marks are formed by a single recording pulse, but the recording pulse level of 3T and 4T, that is, the recording power is higher than the mark level of 5T or more. It is getting bigger. Specifically, the recording power ratio of the 3T mark, the 4T mark, and the mark having a length of 5T or more is determined to be constant.

  When recording is performed with a recording pulse waveform having one type of recording power or a fixed ratio of recording power, the modulation rate increases as the recording speed increases. However, if the modulation degree becomes excessive, there is a high possibility that an AR (Aperture Ratio), an LPP error, an ADIP error, etc. will be adversely affected. Further, the asymmetry in which thermal interference occurs is close to the standard value or the lower limit of the reproducible range, and the margin is narrowed.

JP 2003-77128 A JP 2003-85753 A

  Examples of the problem to be solved by the present invention are as described above. An object of the present invention is to provide an information recording apparatus, an information recording method, and an information recording program capable of recording information with less waveform distortion with an appropriate modulation degree and high asymmetry even during high-speed recording.

  In one embodiment of the present invention, an information recording apparatus for forming a recording mark corresponding to a recording signal by irradiating a recording medium with laser light includes: a light source that emits the laser light; and the light source based on the recording signal And a test writing means for performing test writing by driving the light source based on the recording pulse signal, and the recording pulse signal forms the recording mark. The test writing means performs test writing by changing the recording power of the short mark while keeping the recording power of the long mark constant, and a space period in which the recording mark is not formed.

  The information recording apparatus records information by irradiating a recording medium such as DVD-R / RW or DVD + R / RW with a laser beam to form a recording mark corresponding to the recording signal. The recording pulse signal for forming the recording mark corresponding to the recording signal has a mark period for forming the recording mark and a space period for not forming the recording mark. In test writing (test recording) performed prior to actual information recording, the recording power of the long mark is made constant and the recording power of the short mark is changed. Thereby, the recording power of the short mark is appropriately determined so as to obtain desired recording characteristics. Further, actual recording is performed using the recording power thus determined.

  In one aspect of the information recording apparatus, the recording power of the long mark can be a recording power that ensures reproduction compatibility. In a particularly preferred embodiment in that case, the recording power of the long mark is The recording power can be set such that the modulation degree falls within a predetermined range.

  In another aspect of the information recording apparatus, the recording power of the long mark may be a recording power at which waveform distortion is a predetermined value or less.

  In another aspect of the information recording apparatus, the recording power of the short mark may be a recording power with an asymmetry in the range of −0.05 to 0.15. In another aspect, the recording power of the short mark may be a recording power at which the β value is zero.

  In another aspect of the information recording apparatus, the test writing unit includes a unit for reading a recording mark formed by the test writing, and an asymmetry and / or a β value obtained based on the read recording mark. Test writing is repeated until a predetermined condition is satisfied. Thereby, it is possible to obtain an appropriate recording power having predetermined conditions.

  In a preferred embodiment of the information recording apparatus, the short mark may be a shortest mark, and the long mark may be a mark other than the short mark. In another preferred embodiment, the short mark may be the shortest mark and the second shortest mark, and the long mark may be a mark other than the short mark. In still another preferred embodiment, the short mark may be a mark whose level does not have the maximum amplitude, and the long mark may be a mark whose level has the maximum amplitude.

  In another embodiment of the present invention, an information recording method for forming a recording mark corresponding to a recording signal by irradiating a recording medium with a laser beam generates a recording pulse signal for driving the light source based on the recording signal. And a test writing step of performing test writing by driving the light source based on the recording pulse signal, wherein the recording pulse signal includes a mark period for forming the recording mark, and the recording mark. In the trial writing process, the long mark recording power is kept constant, and the short mark recording power is changed to perform trial writing.

  According to the above information recording method, as in the above information recording apparatus, an appropriate recording power for realizing a desired asymmetry and / or β value can be determined.

  In another embodiment of the present invention, an information recording program that is executed in an information recording apparatus including a light source and forms a recording mark corresponding to a recording signal by irradiating a recording medium with a laser beam is based on the recording signal. The information recording apparatus executes a signal generation step for generating a recording pulse signal for driving the light source and a test writing step for driving the light source based on the recording pulse signal to perform test writing. The pulse signal includes a mark period in which the recording mark is formed and a space period in which the recording mark is not formed, and the test writing process changes the recording power of the short mark while keeping the recording power of the long mark constant. Trial writing.

  By executing the above information recording program in the information recording apparatus, the above-described information recording apparatus can be realized.

It is a figure which shows the recording pulse waveform by 1st Example of this invention. It is a figure explaining a modulation degree and asymmetry. It is a figure explaining the definition of waveform distortion (distortion rate). It is a graph which shows the relationship between recording power, a modulation degree, and a distortion rate. An example of a reproduction RF signal waveform of data recorded by the conventional recording method and the recording method of the embodiment is shown. It is a figure which shows the definition of (beta) value typically. It is a figure which shows the recording pulse waveform by 2nd Example. It is a figure which shows the recording pulse waveform by 3rd Example. It is a block diagram which shows schematic structure of the information recording / reproducing apparatus to which this invention is applied. It is a block diagram which shows the structure of the recording control part shown in FIG. It is a block diagram which shows the structure of LD driver shown in FIG. It is a graph which shows the relationship between the drive current of LD, and output power. It is a flowchart of the recording condition determination process by an Example. It is a flowchart of the recording process by the information recording / reproducing apparatus of an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Information recording / reproducing apparatus 2 Optical pick-up 3 Spindle motor 10 Recording control part 12 LD driver 13 APC circuit 14 Sample hold circuit 15 Controller 16 Front monitor diode 20 Reproduction control part 30 Servo control part

  The present invention separately sets the recording power of the long mark and the short mark in an information recording apparatus that records information by driving a laser light source with a recording pulse signal. Then, the recording power of the long mark is fixed, and trial writing is performed while changing the recording power of the short mark, and the optimum recording power of the short mark is determined.

[First embodiment]
First, a first embodiment of the present invention will be described. In the following description, the recording power of the short mark and the long mark will be described prior to the embodiment in which the trial writing is performed.

  FIG. 1 shows a recording pulse waveform (write strategy) according to the first embodiment of the present invention. For comparison, the recording pulse waveform at the time of 8 × speed recording of a normal DVD-R is shown in the upper part of FIG. 1, and the recording pulse waveform according to the first embodiment is shown in the lower part of FIG.

  In FIG. 1, the recording data includes a mark period Twd having a length corresponding to the recording data length and a space period Tsp having a length corresponding to the recording data length. In the present invention, the length of the space period is not a problem, and a part thereof is not shown.

  In the DVD-R, marks having a length of 3T and 4T are formed by a recording pulse waveform composed of a single pulse, and a mark having a length of 5T or more is composed of a top pulse 60tp, a last pulse 60lp, and an intermediate bias portion 60m. Formed by a substantially concave recording pulse waveform. Specifically, as shown in the upper part of FIG. 1, in DVD-R 8 × recording, 3T and 4T recording pulse waveforms are a period of bias power Pb, a period of peak power Po, and a period of zero level. And have. The recording pulse waveform of 5T or more has a period of bias power Pb, a top pulse period 60tp and a last pulse period 60lp of peak power Po, a period 60m of intermediate bias power Pm, and a period of zero level. Here, as shown in the figure, in the recording pulse waveform at the time of 8 × speed recording of a normal DVD-R, the power of the 3T and 4T marks, and the recording power of the top pulse and the last pulse of the mark of 5T or more (these Are also referred to as “peak power Po”).

  In this specification, “recording power” is a concept including peak power and intermediate bias power. That is, when the recording pulse waveform is 3T and 4T marks in FIG. 1, the recording power is only the peak power, but when the recording pulse waveform is 5T marks or more, the recording power indicates the peak power and the intermediate bias power.

  On the other hand, in the present invention, the recording power of the long mark is made different from the recording power of the short mark. In the first embodiment, “short mark” refers to the shortest mark and the second shortest mark, and “long mark” refers to a mark other than the short mark. That is, the short mark is a 3T and 4T mark, and the long mark is a mark having a length of 5T or more.

  That is, as shown in the lower part of FIG. 1, the peak power Po1 of the recording pulse waveform of the 3T mark and the peak power Po2 of the recording pulse waveform of the 4T mark are different from the peak power Pon of the recording pulse waveform of the mark of 5T or more. . The peak power Pon of a mark of 5T or more is the same regardless of the length of the mark.

  In FIG. 1, the peak power Po1 of the 3T mark is larger than the peak power Po2 of the 4T mark, but this is an example, and the present invention is not limited to this. Therefore, the peak power Po1 of the 3T mark and the peak power Po2 of the 4T mark may be the same, or one may be larger than the other. However, in any case, the peak power Po1 of the 3T mark and the peak power Po2 of the 4T mark are different from the peak power Pon of the mark of 5T or more.

  Next, a method for determining the recording power of the short mark and the long mark will be described. In this embodiment, the recording power is determined in consideration of the modulation degree, asymmetry, waveform distortion, and β value as the recording state evaluation parameters.

  FIG. 2 conceptually shows the modulation factor and asymmetry. “Modulation degree” refers to the amplitude of an RF signal (RF signal obtained by photoelectrically converting return light from a recording medium and including a DC component) obtained by reading data recorded on the recording medium, and RF This is the ratio of the difference between the zero level and the peak level of the signal. FIG. 2 shows an example of an RF signal waveform obtained by reproducing the recording medium. That is, the modulation degree is a ratio of the RF signal amplitude I14 and the difference I14H between the zero level and the peak level, and is given by the following equation.

Modulation rate = I14 / I14H (1)
In general, if the formation of recording marks on the recording medium is insufficient, the degree of modulation becomes low and the influence of noise on the reproduction signal becomes large. Therefore, the S / N ratio is lowered, and the reproduction compatibility is adversely affected. Note that “reproducing compatibility” means that a recording medium recorded by a certain recording device can be properly reproduced by another reproducing device.

  “Asymmetry” refers to the position of the shortest mark with respect to a predetermined long mark giving the maximum amplitude in the RF signal reproduced from the recording medium, and is specifically given by the following equation.

Asymmetry = {(I14H + I14L) / 2- (I3H + I3L) / 2} / I14 (2)
That is, as shown in FIG. 2, the intermediate level between the RF signal levels I14H and I14L corresponding to a predetermined long mark (14T mark) and the intermediate level between the RF signal levels I3H and I3L corresponding to the shortest mark. The positional relationship is shown.

  FIG. 3 schematically shows the definition of waveform distortion (distortion rate). In FIG. 3, the waveform distortion is the ratio of the distortion amount D to the amplitude W of the RF signal. The distortion amount indicates the difference between the level LL that should be originally taken and the level that actually appears in the RF signal waveform. In FIG. 3, a broken line graph 70 is an RF signal waveform when there is no distortion, and the distortion amount is “0”. The graph 70a is an example of an RF signal waveform in which distortion has occurred, and the amount of distortion is given by Da. A graph 70b is another example of an RF signal waveform in which distortion occurs, and the distortion amount is given by Db. As shown in the graphs 70a and 70b, the waveform distortion is also the difference between the level at which the RF signal waveform temporarily becomes substantially flat (that is, the slope is almost zero) and the level LL to be originally taken. Can do.

  FIG. 3 shows an example in which distortion occurs on the bottom level side of the RF signal waveform. However, distortion may occur on the peak level side of the RF signal waveform. The distortion rate in this embodiment is a target in any case.

  FIG. 7 schematically shows the definition of the β value. The β value is a parameter indicating the amount of deviation between the average level of the RF signal and the center value of the amplitude level of the RF signal (center value of all marks). The average level of the RF signal can be obtained, for example, by passing the RF signal through the LPF. Further, the center value of the amplitude level of the RF signal can be obtained by calculation from the minimum level and the maximum level of the RF signal corresponding to the reproduced recording data. The β value is preferably as close to “0”, that is, as the deviation between the average level of the RF signal and the center value of the amplitude level of the RF signal is small.

Next, a method for determining the recording power of the long mark and the short mark will be described. First, the recording power of the long mark will be described. In this embodiment, the recording power of the long mark is
(Condition A) The recording power is within a range that can ensure reproduction compatibility.
(Condition B) Recording power at which waveform distortion does not occur or becomes a predetermined value or less,
(Condition C) A recording power having both Condition A and Condition B is assumed.
There are three methods.

  First, condition A regarding reproduction compatibility will be described. FIG. 4 shows the relationship between the recording power, the modulation degree, and the distortion rate. As shown in the figure, the degree of modulation increases as the recording power increases, but the increase is saturated at a certain recording power. In the DVD standard, in order to ensure reproduction compatibility, the modulation degree is required to be 60% or more, and no upper limit is defined.

  However, as the modulation degree increases, there is a higher possibility that the LPP error rate and AR in the case of DVD-R and the ADIP error rate in the case of DVD + R and the like will be adversely affected. AR indicates the aperture ratio of the LPP detection waveform in DVD-R, and is an indicator of whether LPP can be detected correctly. The LPP error rate indicates the error rate of the LPP signal in the reproduction RF signal. As described above, in order to ensure reproduction compatibility, it is desirable that the modulation degree be 60% or more. However, if the modulation degree is excessively large, the pit width formed on the groove of the recording medium becomes large. The LPP formed adjacent to the groove may become unreadable. This deteriorates the AR and LPP error rates. Also in the case of DVD + R, if the degree of modulation becomes too large, the formed pits become too large, and pre-addresses or the like recorded in advance on the disc cannot be read. This deteriorates the ADIP error rate and the like.

  Also, if the modulation degree is large, the thermal influence on other adjacent marks, particularly short marks, increases, and the recording characteristics deteriorate due to thermal interference or the like. Furthermore, as shown in FIG. 4, since the amount of change in the modulation degree with respect to the change in recording power becomes small, for example, when the modulation degree is used for characteristic detection, such as ROPC (Running Optimum Power Control) Accuracy is reduced.

  As described above, if the degree of modulation is too large, various problems may occur. Therefore, it is desirable to make the modulation degree as small as possible within a range where reproduction compatibility is maintained, for example, about “0.6” (60%). Further, from the viewpoint of preventing the above various problems, in FIG. 4, it is desirable that the upper limit of the modulation degree is about “0.8” (80%). From the above, it is desirable that the peak power Pon of the long mark be in a range in which reproduction compatibility is maintained, and specifically, a value in which the modulation degree is in the range of about 0.6 to 0.8. In particular, it is desirable that the degree of modulation is about 0.6.

  Next, the condition B regarding waveform distortion (distortion rate) will be described. Although the waveform distortion varies depending on the recording conditions and the recording medium, in the example of FIG. 4, the distortion rate increases as the recording power decreases. As the distortion rate increases, the recording characteristics deteriorate. Therefore, it is desirable that the peak power Pon of the long mark is determined so that waveform distortion does not occur or is sufficiently small (for example, 10% or less). Note that the distortion rate graph shown in FIG. 4 is merely an example, and depending on the recording conditions and the recording medium, the distortion rate may increase as the recording power increases.

  From the above, as shown in condition C, it is most desirable to determine the recording power of the long mark so that the condition A related to reproduction compatibility and the condition B related to waveform distortion are simultaneously satisfied.

  Next, a method for determining the recording power of the short mark will be described. FIG. 5 is a waveform diagram for comparing the influence of thermal interference between the case of the conventional method and the case of this embodiment. FIG. 5A shows a reproduction RF signal waveform when a mark of all lengths is formed with the same recording power as shown in the upper part of FIG. On the other hand, FIG. 5B shows a reproduction RF signal waveform when the short mark (3T and 4T) and the long mark (5T or more) are formed with different recording powers as shown in the lower part of FIG. In either case, the asymmetry is within the proper range.

  As shown in FIG. 5A, the level of the waveform of the 3T mark fluctuates due to the influence of thermal interference, and a waveform like a thin whiskers is generated. As a result, the recording characteristics (jitter) are deteriorated even though the asymmetry is in the proper range.

  In contrast, as shown in FIG. 5B, in the case of the present embodiment, the influence of thermal interference does not occur on the waveform of the 3T mark. In this way, by recording with different recording powers for the short mark and the long mark, the power for recording the long mark can be reduced compared to the case where all the marks are recorded with the same recording power as in the prior art. The thermal influence on the short mark can be reduced, and the short mark can be recorded within a range where no thermal interference occurs. That is, as in this embodiment, the recording power of the short mark is made different from the recording power of the long mark, and the peak powers Po1 and Po2 of the short mark are set to appropriate asymmetry (for example, −0.05 to 0 according to the DVD standard). .15) is desirably determined within the range.

  The β value described above can be used as a parameter for determining an appropriate recording power for the short mark. In this case, it is preferable to determine the recording power of the short mark so that the β value becomes a value within a predetermined range close to “0”.

  Next, trial writing according to the first embodiment will be described. In the present invention, in order to determine better recording conditions for each recording medium, test writing is performed by changing the recording power of the short mark while fixing the recording power of the long mark, that is, the peak power and the intermediate bias power. Recording) to determine the optimum short mark recording power. The parameter used when determining the recording power of the short mark is at least one of asymmetry and β value as described above.

  The state of trial writing according to the first embodiment is schematically shown in the upper part of FIG. In the first embodiment, as described above, the shortest mark (3T mark) and the second shortest mark (4T mark) are defined as short marks, and the other marks are defined as long marks. Therefore, in the test writing, the recording power of the mark of 5T mark or higher, that is, the peak power Pon and the intermediate bias power Pmn are set to constant values as shown in FIG.

  Note that the peak power Pon and the intermediate bias power Pm of the long mark used in the trial writing are determined in advance independently of the recording power of the short mark by various known methods, and are stored in, for example, a controller described later. Has been.

  As shown in FIG. 7, in the trial writing, the recording power of the short mark, that is, the 3T mark and the 4T mark is gradually changed. In the example of FIG. 7, the peak power Po1 of the 3T mark starts from Pon and is gradually increased. Similarly, the peak power Po2 of the 4T mark starts from Pon and is gradually increased. Thus, trial writing is performed on the recording medium while gradually changing the recording power of the short mark from a predetermined initial value.

  Then, the test-recorded recording data is read, and parameters such as asymmetry and β value are calculated and evaluated. The test writing is repeatedly executed until parameters such as asymmetry and β value obtained by reproducing the test-written data satisfy a predetermined condition. Thereby, the optimum recording power (peak power Po1, Po2, etc.) of the short mark is determined.

  Specifically, in the example of FIG. 7, in the first trial writing, the peak power of the 3T mark is Po1 (= Pon), the peak power of the 4T mark is Po2 (= Pon), and the peak peak of the 5T mark or more. Test writing with power Pon. In the second trial writing, trial writing is performed with the peak power of the 3T mark as Po1a, the peak power of the 4T mark as Po2a, and the peak power of the 5T mark or more as Pon. Further, in the third trial writing, the trial writing is performed by setting the peak power of the 3T mark as Po1b, the peak power of the 4T mark as Po2b, and the peak power of the 5T mark or more as Pon. Thus, trial writing is repeatedly executed until a recording power that satisfies a predetermined condition is obtained.

  In the example of FIG. 7, the power value for starting trial writing of the short mark is made to coincide with the peak power Pon of the long mark that has already been determined, but the application of the present invention is not limited to this. That is, the short mark trial writing may be started from a value smaller than the peak power Pon of the long mark.

  In the example of FIG. 7, the recording power of the short mark is increased stepwise in a plurality of test writings. Conversely, the recording power may be decreased stepwise from a predetermined initial power value. Good.

  The recording data used in the trial writing includes the following. First, a random pattern including data equivalent to that during actual recording can be used as recording data for trial writing. By using this random pattern, asymmetry and β value can be obtained as evaluation parameters for trial writing.

  In addition, actual data including the data address can be used as recording data for trial writing. In this case, the asymmetry and β value can be obtained in the same manner as described above, and the data error rate can be obtained.

  In addition, among patterns included in the data, a specific pattern in which the detection sensitivity of a value related to the evaluation parameter of the trial writing increases can be used as the trial writing recording data. As an example of the specific pattern, there is a pattern composed of repetition of a shortest mark / space (3T mark / 3T space) and a mark / space giving a maximum amplitude (for example, 11T mark / 11T space). According to this, asymmetry and β value detection sensitivity can be improved as compared with the case of using the above random pattern and actual data.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. The second embodiment differs from the first embodiment only in the method for defining the long mark and the short mark. The lower part of FIG. 7 shows the recording pulse waveform in the second embodiment. As shown in the figure, in the first embodiment, the shortest mark (3T) and the second shortest mark (4T) are defined as short marks, and the other marks (5T or more) are defined as long marks. Then, test writing was performed by fixing the recording power of the long mark and changing the peak powers Po1 and Po2 of the short mark.

  In contrast, in the second embodiment, only the shortest mark (3T) is defined as a short mark, and other marks (4T or more) are defined as long marks. Therefore, as shown in the figure, the peak power Pon and the intermediate bias power Pm of the long mark 4T or higher mark are fixed, and the test writing is performed by changing the peak power Po1 of the 3T mark, which is the short mark.

  The method for determining the recording power of the short mark by trial writing is the same as in the first embodiment. That is, the peak power Po1 of the short mark is determined so that the asymmetry and / or the β value falls within an appropriate range.

[Third embodiment]
Next, a third embodiment will be described. The third embodiment also differs from the first embodiment only in the method for defining the long mark and the short mark. FIG. 8 shows a recording pulse waveform diagram in the third embodiment. 8 shows the recording pulse waveform when the 6T mark does not have the maximum amplitude, and the lower stage shows the recording pulse waveform when the 6T mark has the maximum amplitude.

  In the third embodiment, a mark whose RF signal waveform does not have the maximum amplitude is defined as a short mark, and a mark whose RF signal waveform has the maximum amplitude is defined as a long mark. However, whether or not a certain mark has the maximum amplitude may vary depending on the recording conditions and the recording medium. Usually, the 3T to 5T marks do not have the maximum amplitude, and the marks greater than or equal to the 7T mark have the maximum amplitude, but the 6T mark may or may not have the maximum amplitude. Therefore, when the 6T mark does not have the maximum amplitude, the 3T to 6T mark is defined as a short mark, and the 7T mark or more is defined as a long mark (see the upper part of FIG. 7). On the other hand, when the 6T mark has the maximum amplitude, the 3T to 5T mark is defined as a short mark, and the 6T mark or more is defined as a long mark.

  Specifically, as shown in the upper part of FIG. 8, when the 6T mark does not have the maximum amplitude, the mark that does not have the maximum amplitude, that is, the 3T mark to the 6T mark are defined as the short mark, and other marks (7T The above is defined as a long mark. Therefore, as shown in the figure, the peak power Pon and the intermediate bias power Pmn of the long mark 7T or more mark are fixed. For the 3T mark to 6T mark, which are short marks, trial writing is performed by changing the peak powers Po1 to Po4 of the top pulse 60tp and the last pulse 60lp. Further, as shown in the figure, for the 5T mark and 6T mark, test writing is performed while simultaneously changing the power Pm3 and Pm4 of the intermediate bias unit 60m.

  On the other hand, as shown in the lower part of FIG. 8, when the 6T mark has the maximum amplitude, marks that do not have the maximum amplitude, that is, 3T marks to 5T marks are defined as short marks, and other marks (6T or more) are defined. It is defined as a long mark. Therefore, as shown in the figure, the peak power Pon and the intermediate bias power Pmn of the mark of 6T or more which is a long mark are fixed. For the 3T mark to 5T mark, which are short marks, trial writing is performed by changing the peak powers Po1 to Po5 of the top pulse 60tp and the last pulse 60lp. Further, as shown in the figure, for the 5T mark, trial writing is performed while simultaneously changing the power Pm3 of the intermediate bias unit 60m.

  The method for determining the recording power of the short mark by trial writing is the same as in the first embodiment. That is, the peak powers Po1 to Po4 and the intermediate bias powers Pm3 to Pm4 of the short mark are determined so that the asymmetry and / or the β value falls within an appropriate range.

[Example of information recording / reproducing apparatus]
FIG. 9 schematically shows the overall configuration of an information recording / reproducing apparatus to which the present invention is applied. The information recording / reproducing apparatus 1 is an apparatus for recording information on the optical disc D and reproducing information from the optical disc D. As the optical disk D, various optical disks including, for example, DVD-R / RW, DVD + R / RW, and the like can be used.

  An information recording / reproducing apparatus 1 includes an optical pickup 2 that irradiates a recording beam and a reproducing beam onto an optical disc D, a spindle motor 3 that controls rotation of the optical disc D, and a recording control unit that controls recording of information on the optical disc D. 10, a reproduction control unit 20 that controls the reproduction of information already recorded on the optical disk D, a spindle servo that controls the rotation of the spindle motor 3, and a focus servo that is a relative position control of the optical pickup 2 with respect to the optical disk D And a servo control unit 30 for performing various servo controls including a tracking servo.

The recording control unit 10 receives a recording signal, generates a drive signal _SD for driving a laser diode in the optical pickup 2 by a process described later, and supplies this to the optical pickup 2.

  The reproduction control unit 20 receives the read RF signal Srf output from the optical pickup 2, generates a reproduction signal by performing predetermined demodulation processing, decoding processing, and the like on the read RF signal Srf.

  The servo control unit 30 receives the read RF signal Srf from the optical pickup 2 and supplies a servo signal S1 such as a tracking error signal and a focus signal to the optical pickup 2 based on the read RF signal Srf, and also supplies the spindle servo signal S2 to the spindle motor 3. To supply. As a result, various servo processes such as tracking servo, focus servo, and spindle servo are executed.

  Note that the present invention mainly relates to a recording method in the recording control unit 10, and various known methods can be applied to reproduction control and servo control, so detailed description thereof will not be given.

  FIG. 9 illustrates an information recording / reproducing apparatus as one embodiment of the present invention, but the present invention can also be applied to a recording-only information recording apparatus.

  FIG. 10 shows the internal configuration of the optical pickup 2 and the recording control unit 10. As shown in FIG. 10, the optical pickup 2 includes a laser beam LD for generating a recording beam for recording information on the optical disc D and a reproduction beam for reproducing information from the optical disc D, and an emission from the laser diode LD. And a front monitor diode (FMD) 16 that receives the laser beam and outputs a laser power level signal LDout corresponding to the laser beam.

  In addition, the optical pickup 2 receives a reflected beam of the reproduction beam from the optical disk D and generates a read RF signal Srf, and guides the recording beam, the reproduction beam, and the reflected beam in appropriate directions. However, the illustration and detailed description thereof are omitted.

  On the other hand, the recording control unit 10 includes a laser diode (LD) driver 12, an APC (Automatic Power Control) circuit 13, a sample hold (S / H) circuit 14, and a controller 15.

  The LD driver 12 supplies a current corresponding to the recording signal to the laser diode LD to record information on the optical disc D. The front monitor diode 16 is disposed in the vicinity of the laser diode LD in the optical pickup 2, receives the laser light emitted from the laser diode LD, and outputs a laser power level signal LDout indicating the level.

  The sample hold circuit 14 samples and holds the level of the laser power level signal LDout at a timing defined by the sample hold signal APC-S / H. The APC circuit 13 controls the power of the LD driver 12 based on the output signal of the sample and hold circuit 14 so that the bias power level of the laser light emitted from the laser diode LD is constant.

The controller 15 mainly performs a recording operation and an APC operation. First, the recording operation will be described. In the recording operation, the controller 15 generates switch switching signals SW _R , SW _W1 and SW _W2 for controlling the amount of current supplied to the laser diode LD, and the control signal Svr, and supplies them to the LD driver 12.

  FIG. 11 shows a detailed configuration of the LD driver 12. As shown in FIG. 11, the LD driver 12 includes a current source 17R for bias level, current sources 17W1 and 17W2 for write level, and switches 18R, 18W1 and 18W2.

Current source 17R for the bias level is the current source for supplying a drive current I _R for emitting a laser beam at the bias power Pb to the laser diode LD, the driving current I _R is supplied to the laser diode LD through the switch 18R Is done. Thus, turning on the switch 18R is supplied drive current I _R of the bias power to the laser diode LD, the supply of the drive current I _R and to turn off the switch 18R is stopped. The magnitude of the drive current I _R from the current source 17R varies depending on the control signal S _APC .

The light level current sources 17W1 and 17W2 are current sources for supplying drive currents I _W1 and I _W2 for causing the laser diode LD to emit laser light with write power, respectively. The drive current I _W1 is supplied to the laser diode LD via the switch 18W1, and the drive current I _W2 is supplied to the laser diode LD via the switch 18W2.

In the write strategy according to the present invention, two levels of write power are used: a first write power (peak power) Po and a lower second write power (intermediate bias power) Pm (see FIG. 1, etc.). . When the switch 18W1 is turned on with the switch 18R turned on, the total drive current of the drive currents I _R and I _W1 is supplied to the laser diode LD, thereby driving the laser diode with the second write power Pm. . Further, when the switch 18W2 is further turned on while the switches 18R and 18W1 are turned on, the laser diode LD is further supplied with the drive current I _W2 , and as a result, the laser diode is supplied with the drive currents I _R , I _W1 and I The total drive current of _W2 flows and the laser diode is driven with the first write power Po. When the switch 18W1 is turned off, the supply of the drive current I _W1 is stopped, and when the switch 18W2 is turned off, the supply of the drive current I _W2 is stopped. A control signal Svr is supplied from the controller 15 to the current source 17W2, and the current source 17W2 supplies a drive current I _W2 corresponding to the control signal Svr to the laser diode LD.

FIG. 12 shows the relationship between the drive current supplied to the laser diode LD and the output power of the laser light emitted from the laser diode LD. As can be seen from FIG. 12, a drive current is supplied I _R to the laser diode LD, the laser beam is emitted at a bias power Pb. When the drive current I _W1 is further applied in this state, the laser light is emitted with the second write power Pm. Further, when the drive current I _W2 is further applied, the laser light is emitted with the first write power Po.

When recording information on the optical disk, basically, the drive current I _R is always supplied, the laser beam is emitted with the bias power Pb, and the drive currents I _W1 and I _W2 are added according to the recording pulse. The first write power Po or the second write power Pm is applied, and information is recorded on the optical disc.

  Further, the first write power (peak power) Po changes according to the control signal Svr supplied from the controller 15. As shown in FIG. 10, the controller 15 receives the recording signal, determines whether each recording data included in the recording signal is a short mark or a long mark, and sends the control signal Svr to the current source 17W2 according to the result. To supply. Thereby, when the recording data is a long mark, the current source 17W2 is controlled so that the first write power Po becomes a constant peak power Pon, and when the recording data is short data, the first The current source 17W2 is controlled so that the write power Po becomes a peak power Po1, Po2, etc. different from the constant peak power Pon. Thereby, as shown in the above embodiments, the recording power of the short mark and the long mark can be made different. Note that the discrimination between the short mark and the long mark by the controller 15 is different in each of the first to third embodiments as described above.

Next, the APC operation will be described. The APC operation is to adjust the drive current level supplied from the LD driver 12 to the laser diode LD so that the level of the bias power of the laser beam output from the laser diode LD is constant. More specifically, a long space period (for example, 5T to 11T, 14T) of the space portion of the recording signal (8-16 modulated and having a mark period and a space period having a length of 3T to 11T and 14T). During the space period), the drive signal _SD from the recording control unit 10 is adjusted so that the level of the bias power Pb becomes constant.

  Specifically, it operates as follows. The controller 15 generates a recording pulse corresponding to the recording signal as described above, and drives the LD driver 12 with the recording pulse to emit laser light from the laser diode LD.

  The front monitor diode 16 is disposed in the vicinity of the laser diode LD in the optical pickup 2, receives the laser light emitted from the laser diode LD, generates a laser power level signal LDout indicating the level, and supplies it to the sample hold circuit 14. Supply.

  The sample hold circuit 14 samples the laser power level signal LDout supplied from the front monitor diode 16 at a timing given by the sample hold signal APC-S / H input from the controller 15, and holds the level for a predetermined period. . The sample hold signal APC-S / H output from the controller 15 is a pulse indicating a period during which APC is executed (referred to as an “APC period”).

Therefore, the sample hold circuit 14 holds the level of the laser power level signal LDout and supplies it to the APC circuit 13 during the APC period in the space period of the recording signal. The APC circuit 13 supplies the control signal S _APC to the LD driver 12 so that the level of the laser power level signal LDout in the APC period is constant.

The control signal S _APC is input to the bias level current source 17R in the LD driver 12, as shown in FIG. Thus, in accordance with the control signal S _APC, the current I _R changes flowing from the bias level current source 17R. That is, APC is executed so that the bias power level obtained by the laser diode LD is constant.

  Next, recording condition determination processing by the information recording / reproducing apparatus will be described. The recording condition determination process is a process executed prior to actual information recording on the recording medium, and is a process for determining a particularly appropriate recording power in the present invention.

  FIG. 13 shows a flowchart of the recording condition determination process. The recording condition determination process can be realized basically by executing a program prepared in advance by the controller 15 shown in FIG.

  First, the controller 15 determines whether or not a disc exists in the information recording / reproducing apparatus (step S11). This is performed by a known method such as emitting laser light from a light source and detecting the return light. The recording condition determination process does not proceed until the disc is inserted.

  When a disc is detected (step S11; Yes), the controller 15 acquires long mark recording condition information from an internal memory (not shown), for example (step S12). The recording condition information includes recording power, write strategy, and the like. In each of the above-described embodiments, as described above, the recording power (peak power Pon and intermediate bias power Pmn) of the long mark has already been determined and stored in an internal memory or the like. Therefore, the controller 15 reads it.

  Next, the controller 15 performs test writing for determining the recording condition of the short mark. Specifically, first, test writing conditions for short marks are set (step S13). Here, the “short mark trial writing condition” includes a setting range of the recording power of the short mark, that is, an initial value and a changing range of the recording power, a changing step, and the like, and further, asymmetry and β value used as parameters. Including appropriate ranges.

  When the trial writing condition is determined, the controller 15 performs trial writing (step S14). Specifically, signals SWW1, SWW2, SWR, Svr, etc. are supplied to the LD driver 12 so that trial writing is performed with the initial value of the recording power, and trial writing is performed on the disc. Then, the data recorded by the trial writing is read from the disk (step S15), the asymmetry and β value as the evaluation parameters are acquired from the RF signal and the like, and whether or not these values satisfy the target condition. Determination is made (step S16).

  If the target condition is not satisfied (step S16; No), the process returns to step S13, the recording power is changed, and steps S13 to S16 are executed. On the other hand, if the target condition is satisfied (step S16; Yes), the recording condition including the recording power at that time is determined as the optimum recording condition for the short mark (step S17), and the process ends.

  As described above, by the recording condition determination process, the asymmetry and the β value are evaluated while changing the recording power of the short mark, and the recording power giving the appropriate asymmetry and / or β value is determined.

  Next, recording processing by the information recording / reproducing apparatus will be described. The recording process described below is executed mainly by the controller 15 shown in FIG. 10 controlling the LD driver 12 and the like based on a recording signal supplied from the outside. FIG. 14 shows a flowchart of the recording process. The controller 15 can execute the recording process by executing a program prepared in advance corresponding to the process shown below.

  First, when a recording signal including a plurality of recording data is received (step S1), the controller 15 determines whether each recording data included in the recording signal corresponds to a short mark or a long mark. This determination is different in the first to third embodiments as described above. If it is determined that the recording data is a short mark (step S2; Yes), the controller 15 determines a recording power (that is, peak power and intermediate bias power) according to the mark length (step S3). For example, in the case of the first embodiment, if the short mark is 3T, the peak power is determined as Po1, and if it is 4T, the peak power is determined as Po2. The recording power at this time is obtained by the recording condition determination process described above. On the other hand, when it is determined that the recording data is a long mark (step S2: No), the controller 15 sets the recording power to a fixed value (step S4). That is, the peak power and the intermediate bias power are determined as fixed values Pon and Pmn, respectively.

  Then, the controller 15 supplies a control signal Svr corresponding to the recording power determined in step S3 or S4 to the LD driver 12 (step S12). The LD driver 12 drives the laser diode LD based on the supplied control signal Svr, and records a recording mark corresponding to the recording data on the disk D (step S6). Thus, the input recording signal is recorded on the disk D.

[Modification]
In the above embodiment, test writing is performed by changing the recording power of the recording pulse waveform to obtain the optimum recording power. This is done by changing the time width of the recording pulse waveform (that is, the strategy is changed). It can be combined with a method of trial writing. The time width of the recording pulse waveform is changed by, for example, performing test writing while changing the time widths of the top pulse 60tp, the intermediate bias unit 60m, the last pulse 60lp, etc. shown in FIG. Evaluate the evaluation parameters. Then, the strategy whose evaluation parameter satisfies a predetermined condition is determined as the optimum strategy.

  As a combination method with the present embodiment, test writing is performed by changing the recording power according to the present embodiment, and after determining an appropriate recording power of the short mark, the test writing is performed by changing the above-mentioned strategy. What is necessary is just to decide a strategy. Further, if necessary, the trial writing may be performed by changing the recording power again according to the present embodiment. As a result, both the power and time width of the recording pulse waveform can be optimized.

  In the above embodiment, the present invention is applied to DVD-R / RW and DVD + R / RW. However, the present invention is similarly applied to Blu-ray discs, HD DVDs, DVD-RAMs and the like. Can also be applied.

The present invention is used for an information recording apparatus, an information reproducing apparatus, an information recording / reproducing apparatus, and the like that records information on a recording medium such as an optical disk and / or reproduces information from the recording medium by irradiating laser light or the like. can do.

Claims (12)

An information recording apparatus for forming a recording mark corresponding to a recording signal by irradiating a recording medium with a laser beam,
A light source for emitting the laser light;
Signal generating means for generating a recording pulse signal for driving the light source based on the recording signal;
Test writing means for performing test writing by driving the light source based on the recording pulse signal,
The recording pulse signal includes a mark period for forming the recording mark and a space period for not forming the recording mark,
The information recording apparatus according to claim 1, wherein the test writing means performs the test writing by changing the recording power of the short mark while keeping the recording power of the long mark constant.   2. The information recording apparatus according to claim 1, wherein the recording power of the long mark is a recording power that ensures reproduction compatibility.   3. The information recording apparatus according to claim 2, wherein the recording power of the long mark is a recording power having a modulation degree within a predetermined range.   2. The information recording apparatus according to claim 1, wherein the recording power of the long mark is a recording power at which waveform distortion becomes a predetermined value or less.   2. The information recording apparatus according to claim 1, wherein the recording power of the short mark is a recording power having an asymmetry in a range of -0.05 to 0.15.   2. The information recording apparatus according to claim 1, wherein the recording power of the short mark is a recording power with a β value of 0.   The test writing means reads the recording mark formed by the test writing, and repeats the test writing until the asymmetry and / or β value obtained based on the read recording mark satisfies a predetermined condition. The information recording apparatus according to claim 1, characterized in that it is characterized in that:   The information recording apparatus according to claim 1, wherein the short mark is a shortest mark, and the long mark is a mark other than the short mark.   2. The information recording apparatus according to claim 1, wherein the short mark is a shortest mark and a second shortest mark, and the long mark is a mark other than the short mark.   2. The information recording apparatus according to claim 1, wherein the short mark is a mark whose level does not have a maximum amplitude, and the long mark is a mark whose level has a maximum amplitude. An information recording method for forming a recording mark corresponding to a recording signal by irradiating a recording medium with laser light,
A signal generation step of generating a recording pulse signal for driving the light source based on the recording signal;
A test writing step of performing test writing by driving the light source based on the recording pulse signal,
The recording pulse signal includes a mark period for forming the recording mark and a space period for not forming the recording mark,
In the test writing step, the long mark recording power is constant and the short mark recording power is changed to perform test writing. An information recording program that is executed in an information recording apparatus including a light source and irradiates a recording medium with a laser beam to form a recording mark corresponding to a recording signal,
A signal generation step of generating a recording pulse signal for driving the light source based on the recording signal;
A test writing step of performing test writing by driving the light source based on the recording pulse signal, and causing the information recording apparatus to execute the test writing process,
The recording pulse signal includes a mark period for forming the recording mark and a space period for not forming the recording mark,
An information recording program characterized in that the trial writing step performs trial writing by changing the recording power of the short mark while keeping the recording power of the long mark constant.

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